Hot-carrier transistors are a class of devices that leverage the excess kinetic energy of carriers. Unlike regular transistors, which rely on steady-state carrier transport, hot-carrier transistors modulate carriers to high-energy states, resulting in enhanced device speed and functionality. These characteristics are essential for applications that demand rapid switching and high-frequency operations, such as advanced telecommunications and cutting-edge computing technologies. However, their performance has been limited by how hot carriers have traditionally been generated.
A team of researchers, led by Prof. Liu Chi, Prof. Sun Dongming, and Prof. CHeng Huiming from the Institute of Metal Research (IMR) of the Chinese Academy of Sciences, has proposed a novel hot carrier generation mechanism called stimulated emission of heated carriers (SEHC). The team has also developed an innovative hot-emitter transistor (HOET), achieving an ultralow sub-threshold swing of less than 1 mV/dec and a peak-to-valley current ratio exceeding 100. The study provides a prototype of a low power, multifunctional device for the post-Moore era.
Low-dimensional materials like graphene, due to their atomic thickness, excellent electrical and optical properties, and perfect surface without defects, can easily form hetero-structures with other materials. This creates a variety of energy band combinations, offering new possibilities for developing novel hot carrier transistors.
Researchers at IMR developed a hot-emitter transistor using a combination of graphene and germanium, leading to an innovative mechanism for hot carrier generation. This new transistor is composed of two coupled graphene/germanium Schottky junctions.
During operation, germanium injects high-energy carriers into the graphene base, which then diffuse to the emitter, triggering a substantial current increase due to the preheated carriers there. This designs sub-threshold swing of less than 1 mV/dec surpasses the conventional Boltzmann limit of 60 mV/dec.
Meanwhile, this transistor also shows a peak-to-valley current ratio exceeding 100 at room temperature. The potential for multi-valued logic computing has further been demonstrated based on these characteristics.
"This work opens a new realm in transistor research, adding a valuable member to the family of hot carrier transistors and showing broad prospects for their application in future high-performance, low-power, multifunctional devices," said Liu.